With the appearance of Volume 5 (of a projected 12 volumes) of this series, reviewers are running out of superlatives. To embark upon the task of producing a fully illustrated handbook covering every species of bird in the world is audacious enough; to actually bring it off at the level of quality established in this series will be an incredible accomplishment. At this point, the odds of completing the series sometime near the target of 2010 look very promising indeed. Not only is the book comprehensive and authoritative, it is also beautiful. Despite the wealth of detailed information that is de rigueur in a work of this sort, the text, especially the lengthy treatments of each of the families, is very readable in spite of being packed with interesting facts.

This volume covers the families Tytonidae (barn-owls; 16 species), Strigidae (true owls; 189 species), Steatornithidae (Oilbird; 1 species), Aegothelidae (owlet-nightjars; 9 species), Podargidae (frogmouths; 12 species), Nyctibiidae (potoos; 7 species), Caprimulgidae (nightjars; 89 species), Apodidae (swifts; 92 species), Hemiprocnidae (tree-swifts; 4 species), and Trochilidae (hummingbirds; 328 species). Several of these are difficult groups. The nocturnal owls, nightjars, and allies often are poorly known, and very few species have been studied in detail. In these groups, as well as in the swifts and hummingbirds, the relationships of genera and species limits are not well understood.

As with previous volumes, this one contains a foreword dealing with some general topic. In this case, Nigel Collar discusses risk indicators and status assessment in birds. He describes, with examples, the IUCN system for classifying the conservation status of bird populations. After discussing the criteria used to identify species at risk, Collar concludes that "…the single most important perception that follows from the criteria…is that the majority of extinction-prone species can only be secured by protected areas, many of them large, many of them strict; only, in other words, by setting aside significant tracts of the planet with the full intention that the factors rendering their inhabitants extinction-prone shall be absolutely minimized" (p.26). This, of course, is not news, but perhaps if we repeat it enough times we will someday actually do something about it. It is possible that he thought the connection so self evident as to require no explicit comment, but I think it unfortunate that he made no mention whatsoever of unrestrained growth in the human population, the direct cause of exacerbating factor in virtually all of the problems faced by bird populations that are at risk.

Each family is introduced with a lengthy discussion that includes information on the fossil record and taxonomic history of the family, morphology, habitats occupied, general habits with many specific examples, voice, food and feeding habits, breeding behavior and ecology, movements, relationships with humans (an eclectic collection that is fun to read), and status and conservation. These family accounts are heavily illustrated with stunning photographs that are not only technically superb in nearly all cases, but also illustrate a vast array of interesting aspects of the biology of these birds. The photos are not just present as pretty pictures (though they are surely that), because most of them make some salient point related to the accompanying text. Simply locating all of these photographs must have been a daunting task. Given that many of the species treated in this volume are nocturnal and poorly known, it is remarkable that such excellent images even exist. Many rare photos and photos of rare species appear: Congo Bay-Owl (Phodilus prigoginei), a species with only two definite records from a single locality; Long-whiskered Owlet (Xenoglaux loweryi), a cloud-forest endemic discovered in Peru in 1977; Sokoke Scops-Owl (Otus ireneae); Seychelles Scops-Owl (O. insularis); Comoro Scops-Owl (O. pauliani), known only from the type specimen and a few photos; the only known photo of Javan Scops-Owl (O. angelinae); Forest Owlet (Athene blewitti), rediscovered in 1998 in India; Puerto Rican Nightjar (Caprimulgus noctithersus); Scissor-tailed Hummingbird (Hylonympha macrocerca) of northeastern Venezuela; Juan Fernandez Firecrown (Sephanoides fernandensis); and numerous others. As others reviewers have noted, these volumes easily qualify as beautiful coffee table books as well as serious scientific works.

The species accounts come after the treatment of each family and follow a standard format. French, German, and Spanish common names are provided. Taxonomic notes follow, including reference to the original description (citations provided in a separate reference list). Distribution is described, and if there are recognized subspecies, their ranges are very briefly noted. Each species account is accompanied by a range map. These appear to be generally accurate, but they are small and not detailed. A description is given for sexes and ages, including a verbal description of vocalizations. The descriptions are not designed to facilitate field identification, and little note is made of features that distinguish similar species. Then follow brief descriptions of habitat, food and feeding habits, breeding season, nest, clutch size, etc., movements, and status and conservation. Each account ends with a list of citations by name and date; full references appear in the bibliography. Information on many of these species is scant, so most of the species accounts are short (typically about a half column). The extensively studied and worldwide Barn owl (Tyto alba) merited the longest account in the series so far (one and two-third pages).

The species accounts are accompanied by color plates by 19 artists. Each species is illustrated, and in cases where significant geographic variation or color morphs exist, there may be as many as three or four illustrations per species. Both sexes are depicted when there is significant sexual dimorphism in plumage. The birds are presented in unadorned field-guide type plates, typically in perched poses. Swifts are depicted in flight, and small flight paintings accompany many of the nightjars as well. The plates vary somewhat in accuracy, but overall they are excellent.

In such a massive volume containing so much factual information, there must be a substantial number of errors and omissions. Experts on particular species and groups will no doubt delight in pointing these out. In general, extralimital records are very inconsistently presented. In North America, for example, Texas occurrences of Mottled Owl (Ciccaba virgata) and Stygian Owl (Asio stygius), many records of Plain-capped Starthroat (Heliomaster constantii) in Arizona and Bahama Woodstar (Calliphlox evelynae) in Florida, and Cinnamon Hummingbird (Amazilia rutila) occurrences in Arizona and New Mexico are not mentioned, whereas old and probably invalid Texas records of Rufous-tailed Hummingbird (A. tzacatl) are noted. The Green Violet-ear (Colibri thalassinus) is said to stray to the extreme southwestern United States, when in fact the records are from the central and eastern parts of North America. A bird reported (p. 413, 420 to be a Black Swift (Cypseloides niger) of Caribbean origin from Martha’s Vineyard, Massachusetts, was never identified and may, in fact, have been an Apus (W. Petersen pers. comm.). These are quibbles; the book was not intended to deal with distribution in this detail. However, readers should be warned that this information should be taken with a grain of salt.

The most serious flaw in these volumes, and one that reduces their usefulness, is that references are not cited in the text. Reading the family accounts, one comes across many interesting and provocative statements and fascinating facts that merit further exploration. But the text provides no efficient way to find the source of the information. At the end of each family account appears an extensive list of references, but without titles. The only way to try to ferret out the source of a particular piece of information is to check each of these citations against the bibliography. All but the most persistent readers will throw up their hands in the face of this task. The usefulness of future volumes would be greatly enhanced by using small superscript numerals or some other space-efficient means of connecting information with its source. Approximately 8,000 references are cited, and it is a shame that this vast collection of data is not made more accessible.

This volume, along with its companions, represents a stunning achievement. Collectively, this set of volumes will be the indispensable primary source of information on the birds of the world for the next several decades.

KENNETH P. ABLE, Department of Biological Sciences, State University of New York, Albany, New York 12222, USA.